Search for a new heavy gauge boson in final states with one lepton and missing transverse momentum with the ATLAS detector

The Standard Model (SM) has been an extremely successful theory in describing nature from the fundamental particles and their interactions. Despite the successes of the SM, there are phenomena which cannot be explained by the SM such as dark matter, neutrino mass, and gravity. Hence, various extensions to the SM have been developed during the last few decades, and several theoretical models predict the existence of additional heavy gauge bosons. In this thesis, a search for a new heavy gauge boson in final states with one lepton (electron or muon) and missing transverse momentum is presented using the dataset of proton-proton collisions at a center-of-mass energy of 13 TeV, which were recorded in 2015, 2016, and 2017 by the ATLAS detector at Large Hadron Collider at CERN. No deviation from the Standard Model prediction is observed, and hence exclusion limits on the production cross section times branching ratio, $\sigma(pp\rightarrow W')\times \textrm{BR}(W'\rightarrow\ell\nu)$ and on the Sequential Standard Model $W'$ boson mass are derived exploiting the Bayesian approach. Masses for $W'$ bosons up to 5.6 TeV are excluded by the combination of the electron and muon channels. This marks the most stringent exclusion limit obtained in the $W'$ searches by any collider experiment so far.